1. Field of the Invention
The present invention relates to an automatic screw fastening machine which is capable of securely fastening screws or bolts by applying desired fastening torque without affecting them by inertia inherent in a driver bit at the moment of completing a process for fastening screws or bolts.
2. Prior Art
Conventionally, in order to properly control torque available for fastening screws or bolts, a driver bit is rotated by a rotation drive source such as a motor which can also detect load torque applied to the driver bit via a proper detection means, and then, as soon as the detected value correctly matches a predetermined value, operation of the rotation drive source is brought to a stop. Nevertheless, when executing this conventional method, in particular, when a low value is predetermined for the fastening torque, due to adverse effect of inertia inherent in the rotation drive source, actual fastening torque value exceeds the predetermined value at the moment at which completion of the screw fastening operation is detected. As a result, neither screws nor bolts can be fastened with correct fastening torque.